TTie Nidus of Lunaiia-heroi. 38 



Embryonic Shell of Lunatia-heros. 



The embryos or eggs are very pretty in shape, each measuring 

 about y^ inch in its largest diameter, each cell containing from 

 one hundred to one hundred and twenty-five individual eggs. 

 Quoting again from Dr. Gould's report : "The true nature of the 

 Nidus seems to have been first suspected by Mr. Boys who gave 

 a description and plate of it in the Linnaean Transactions, Vol. 

 V. 230, pi. 10. In the fourteenth volume of the same work Mr. 

 Hogg fully demonstrated its character by hatching from those 

 found on the English coast the young of Natica glaucina." 



Frequently attached to the inner surface of the Nidus are found 

 colonies of little leather-like sacs of nondescript shape a little less 

 than \ inch in length and about ^ inch wide. These sacs are 

 filled with shells almost exactly resembling those of the structural 

 contents of the Nidus, but by micrometrical measurement appear 

 to be a trifle smaller. Each sac contains over one hundred, and 

 they are probably the eggs of some other mollusk which, cuckoo- 

 likc, has taken advantage of the industry of the Lunatia. In this 

 connection it is interesting to remember that many of the mol- 

 lusca, who at maturity are unprovided with a shell or who have 

 only small suggestion of one imbedded in their mantel, have in 

 their embryonic stage a perfect shell which they throw aside soon 

 after the animal escapes from tlie sac. The mollusca, which were 

 probably tlie earliest animal inhabitants of our globe, are often- 

 times peculiarly constituted; both sexes existing in one individual. 

 The gasleropoda, to which class the Lunatia belongs, are frequently 

 hermaphrodite. (By the way, Mr. J. A. Ryder has established the 

 remarkable fact that while in the American Oyster the sexes are 

 separate the European Oysters are hermaphrodite.) 



The Lunatia-heros, the builder of the Nidus, is one of our most 

 common mollusks. The shell varies in size from \ inch upward. 

 Dr. Gould states that he has seen one measuring five inches by 

 three and three-fourths inches. This creature, which seems so ex- 

 ceptionally solicitous for the welfare of its own young, does not 



